The present invention relates to a device for injecting a liquid into a tube having a so-called cannula arranged in said tube whereby, in the fluid injection direction, the cannula has a narrowed section passage, followed by a divergent portion. It is more particularly used for injecting water into a steam generator or boiler and particularly of the vertical penetration single-pass type.
Single-pass, helical steam generators have a pressure resistant envelope containing wound tubes. A first heat transfer fluid, called the primary fluid circulates outside said tube. A secondary fluid passes through the network of tubes and enters through the envelope cover into the tubes via thermal sleeves traversing a tube plate. It then descends via bundles of straight tubes positioned in the central area of the steam generator until reaching the bottom of wound tubes via which it rises and then passes out in vapour form through sleeves traversing the cover periphery.
In such a steam generator, the secondary fluid flow can lead to instability, which particularly occurs under low power operating conditions and which is highly prejudicial to the operation of the apparatus.